1. Field Of The Invention
This invention relates to foot pedal devices for controlling engines such an internal combustion engines, and more particularly, to means for providing control without the need for direct mechanical connection between the pedals and the engines. The invention is particularly directed to providing means and methods for control by wire, i.e., by electrical or electronic means rather than by mechanical links. In the automotive art, accelerator type foot pedals are employed for controlling the flow of fluids to the engines. These usually include a pedal mounting affixed to the vehicle body and a series of links and levers, or bowden wires, connecting the pedal to the carburetor, fuel injector, controller or the like. These link connections usually must be designed to withstand and accommodate engine movements relative to the vehicle frame, as well as to provide accurate control despite such movements. In addition, space must be provided for the linkages to function properly. The choices for routing of the mechanical control rods or wires are limited by their nature. With electrical sensing means directly associated with the pedal, the connection to a carburetor or the like can be accomplished with electrical wiring which relatively speaking, can free the connection problems from the special physical relationships of the older mechanical systems.
Wire type throttle control for motor vehicle engines has been known heretofore. Some construction vehicles, buses and large trucks have used some form or the other for some time. In these instances, however, pedal or other lever control means can be designed without regard to some of the restraints that apply to automobile use. Pedals can be more rugged, higher pedal pressure can be tolerated and less responsive action can be overlooked. Generally, the requirements reflect the usage of the vehicle. For example, the requirement of a system for a rough off-road vehicle would likely reflect its prospective usage. With passenger cars pedal pressures and reaction times are more critical. The pedal system must be one that provides a customary feel and performance for the "typical" driver. Safety of operation with rapid yet controlled return from a high load position to a lower idle position are important considerations, as is the amount of force needed to maintain a desired speed setting. The pedals must function responsively and quickly to the operator's commands and also provide an acceptable non-fatiguing resistance. Drivers are accustomed to applying and releasing pressure on a pedal-like arrangement and become accustomed to the resistance to application of force to the pedal as well as to the rate of withdrawal as the applied pressure is relaxed. With the instant invention, the customary feel during the application of force to increase speed and while maintaining speed, as well as the familiar deceleration movement of the pedal can be duplicated in a wire type control.
With the typical auto, the pedal pressure required when advancing the accelerator pedal is greater than that required to maintain a fixed position. This difference is often referred to as due to the hysteresis effect. This "effect" is important in maintaining the accelerator pedal in position while driving at a relatively constant speed, and it must also be considered in achieving a desired deceleration time. The pressure which must be applied in accelerating is easily borne but if the back pressure of an accelerator spring produced the same effect during the time it was required to retain or maintain speed it would soon become uncomfortable for the operator to maintain a relatively constant speed. The hysteresis effect provides relief. It lessens the load required to maintain a setting of the accelerator yet there is still force to cause reverse pedal action when the foot applied pressure is removed. This invention provides means for insuring a hysteresis effect which will give the desired reduction in pressure while maintaining speed, as contrasted to the resistance experienced in accelerating, and yet with which there will be insured an appropriate force to return the system to idle.